This invention relates to the combination of an I.V. fluid bag (intravenous fluid bag) and a thermally insulating jacket therefor.
As a Certified Registered Nurse Anesthetist (CRNA) I, Robert K. Smith, one of the joint inventors herein, have been interested for several years in the challenge of keeping patients warm in surgery. By carefully monitoring patient temperatures, I have learned that when present operating room techniques are employed, it is not uncommon to see a 2.degree. F. to 4.degree. F. patient body temperature drop from the beginning of anesthetic administration to the time the patient enters the recovery room at the end of the surgery.
Several factors are responsible.
Prior to beginning a surgical procedure, an I.V. line usually is placed in one or more of the patient's veins. Fluid is rapidly infused through this line, in amounts varying from 400 ml. to 1500 ml. This fluid is normally at room temperature, some 28.6.degree. F. less than the patient's normal temperature. This naturally has a pronounced cooling effect on the patient's body temperature.
This adverse effect is aggravated by the fact that, if general anesthesia is applied, the patient is rendered unable to regulate his body temperature.
Furthermore, in some procedures the patient is ventilated with gases which are piped into the operating room from outside the building. These gases are many degrees cooler than the body temperature of the patient. They frequently are administered by an endotrachael tube which bypasses the warming function of the nose.
Still another consideration is the fact that the patient's body is opened, allowing heat to escape. The bigger the opening, the more heat is lost.
It is very important to patient well-being and recovery that his body be maintained at its normal temperature. The patient is much more comfortable if such is the case. If the patient is cold, he will shiver. Shivering greatly increases oxygen consumption.
Furthermore, the patient will metabolize pre-, intra-and post-operatively drugs more rapidly. In sum, if his body temperature is normal he will be more comfortable and recover more rapidly.
Although in the usual situation the patient's body temperature will drop during an operation, there exists a hypermetabolic condition called Malignant Hyperthermia which sometimes occurs during anesthesia. In this condition the patient's temperature rises rapidly to very high levels, 106.degree. to 108.degree. F. or even higher. Part of the treatment of this condition is the rapid administration of cold I.V. fluids. One liter bags of normal saline are kept in the refrigerator of the operating room for this purpose. When these bags are removed from the refrigerator and hung in a room having a temperature of 70.degree. F., they warm rapidly toward the ambient temperature, thus detracting from the efficiency of the treatment.
In both situations, i.e. that in which the patient's body temperature is lowered and that in which it is elevated it would be desirable to provide means for maintaining the temperature of the fluid contents of I.V. fluid bags at the optimum temperature level during the entire period of fluid administration, thereby minimizing, or avoiding entirely, conditions of hypothermia and hyperthermia.
It is the general purpose of the present invention to provide such a means.
Generally stated, the means by which this desired end result is accomplished is the provision, in combination with an I.V. fluid bag, of a thermally insulating jacket which comprises a sheet of thermally insulating material enclosing the bag. Bag support means on the jacket support the bag within the sheet in its bag-enclosing condition. Jacket support means on the jacket support it on an I.V. pole or other support. By preheating or precooling the fluid to the desired level, enclosing the bag in which it is contained in the thermally insulating jacket, and maintaining it within the jacket during the period of fluid administration, the desired result of maintaining the patient body temperature at optimum levels may be obtained.